The present invention is directed to an improved filter for removing contaminants from water.
Over the years, many attempts have been made to provide an effective system for the removal of contaminants from aqueous systems to provide safe drinking water for human consumption.
Such contaminants include organic compounds such as trihalomethanes (e.g., chloroform), as well as inorganic contaminants such as arsenic, cadmium, lead, copper, mercury, chromium and selenium.
Drinking water may also contain various microorganisms such as bacteria, virus, algae, fungus, and protozoa, as well as finely divided and suspended particles derived from soil, silt and inorganic fibers such as asbestos fibers.
For example, ion exchange systems have been employed which employ ion exchange resins such as cation exchange resins to reduce water hardness by exchanging calcium and magnesium for sodium. Chlorine has been found to reduce the effectiveness of such resin materials.
Reverse osmosis has also been employed to remove contaminants by the combined action of osmotic pressure and a selective membrane material. Chlorine frequently is found to have a deleterious effect on such membranes.
Activated carbon has recently achieved much popularity in domestic water purification systems, yet it experiences many drawbacks due to its failure to remove a wide range of contaminants from the water as well as its tendency to quickly become relatively ineffective and/or become contaminated with bacteria.
Combinations of the above systems have also been contemplated.
U.S. Pat. Nos. 4,199,449; 4,759,844; 4,196,081; 4,913,808; 4,826,594; 4,894,154; and 4,430,226 each disclose the combination of an activated carbon material and an ion exchange resin in water purifiers.
U.S. Pat. No. 3,444,079 discloses the combination of a cation exchange resin and activated carbon for demineralizing water.
U.S. Pat. No. 4,561,976 discloses the use of silver-impregnated activated carbon and an anion exchange resin in a water filter.
U.S. Pat. No 4,561,976 discloses the use of three materials in a water purifier consisting of a molecular sieve such as a silicalite, an anion exchange resin and activated carbon (as the last layer).
U.S. Pat. Nos. 4,913,808; 4,430,226; and 4,368,123 disclose the use of admixtures of anion and cation exchange resins in water filters in combination with a bed of activated carbon.
U.S. Pat. No. 4,741,828 discloses the use of silver-impregnated activated carbon as a bactero-statically effective material in water filters.
However, the search has continued in the water purification industry to provide a water purification device which exhibits long life while effectively removing both organic and metallic contaminants from the water.